Problem: Before the previous stop there were 17 people riding on a train. 11 people ended up getting off at the stop. How many people are riding the train now?
Solution: The number riding the train now is the difference between the number who were riding and the number who got off at the previous stop. The difference is $17 - 11$ people on the train. $17 - 11 = 6$ people are on the train.